The compound 2-[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy]methyl]-N-hydroxy-benzenamine of the formula (I) is an important intermediate for preparing inter alia the fungicidal agents such as pyraclostrobin.
EP 0086363 describes a process for producing arylhydroxylamines in high yield with minimal formation of by-product arylamines.
WO 2012/120029 describes a process for the preparation of 2-[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy]methyl] phenyl-hydroxylamine from the correspondingly substituted nitrobenzene compound by reacting the substituted nitrobenzene with hydrogen or hydrazine in the presence of a rhodium catalyst.
WO 1999/012911 describes a method for producing N-acylated (hetero)aromatic hydroxylamine derivatives by hydrogenating a (hetero)aromatic nitro-compound in the presence of a hydrogenation catalyst and in a mixture with an inert, aprotic solvent and an aliphatic amine.
The hydrogenation of nitro-aryl compounds to produce hydroxylamine compounds is not trivial as different side-products may possibly be formed, thereby reducing the yield of the desired hydroxylamine compounds.
According to Figueras, F.; Bernard, Coq. J. Mol. Catal. A: Chem. 2001, 173, 223-230, the selective semi-hydrogenation to a hydroxylamine compound is challenging because precious metal catalyst often reduce nitro compounds all the way to amine compounds. In addition, various other compounds can be formed as side-products. This includes a nitroso compound which is formed by hydrogenolysis of the nitro compound. Further hydrogenation of the nitroso compound gives a hydroxylamine compound. The catalytic hydrogenation of the hydroxylamine compound results in the formation of an amine compound. The first step for the formation of the azoxy compound is the condensation of the nitroso compound and the hydroxylamine compound. Further, the azoxy compound can be hydrogenated to an azo compound, which can be further hydrogenated to give a hydrazo compound. Another problem is that the hydroxylamine compound is unstable and can disproportionate to a nitroso compound, an amine compound and one molecule of water.
It would be highly desirable to have an improved process for the production of the compound of formula (I) which is suitable for industrial use, highly efficient, low-cost, environmentally friendly, and provides a high yield in a short reaction time, thereby overcoming the deficiencies of the prior art. The present subject matter provides such a process.
It is therefore a purpose of the present subject matter to provide a high-yield process for the preparation of 2-[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy]methyl]-N-hydroxy-benzenamine with effective control of the reaction end point.
It is yet another purpose of the present subject matter to provide a process that overcomes the disadvantages of the known art.